Disk drives are information storage devices that use magnetic media to store data and a movable read/write head positioned over the magnetic media to selectively read data from and write data to the magnetic media.
Consumers are constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations. Thus, disk drive manufacturers have continued to develop higher capacity disk drives by, for example, increasing the recording and reproducing density of the information tracks on the disks by using a narrower track width and/or a narrower track pitch. However, each increase in track density requires that the disk drive device have a corresponding increase in the positional control of the read/write head in order to enable quick and accurate reading and writing operations using the higher density disks. As track density increases, it becomes more and more difficult to quickly and accurately position the read/write head over the desired information tracks on the disk. Thus, disk drive manufacturers are constantly seeking ways to improve the positional control of the read/write head in order to take advantage of the continual increases in track density.
One approach that has been effectively used by disk drive manufacturers to improve the positional control of read/write heads for higher density disks is to employ a voice coil motor (VCM). Referring to FIG. 1a, a conventional disk drive device using VCM typically has a drive arm 104, a HGA 106 attached to and mounted on the drive arm 104, a stack of magnetic disks 101 suspending the HGA 106, and a spindle motor 102 for spinning the disks 101. The employed VCM is denoted by reference number 105 and is connected to the drive arm 104 for controlling the motion of the drive arm 104 and, in turn, controlling a slider 103 of the HGA 106 to position with reference to data tracks across the surface of the magnetic disk 101, thereby enabling the read/write head imbedded in the slider 103 to read data from or write data to the disk 101. However, because the inherent tolerances of the VCM 105 and the HGA 106 exist in the displacement of the slider 103 by employing VCM 105 alone, the slider 103 cannot achieve quick and fine position control which adversely impacts the ability of the read/write head to accurately read data from and write data to the disk 101.
In order to solve the problem, an additional actuator, for example a PZT micro-actuator, is introduced in the disk drive device in order to modify or fine tune the displacement of the slider 103. The PZT micro-actuator corrects the displacement of the slider 103 on a much smaller scale, as compared to the VCM, in order to compensate for the resonance tolerance of the VCM and/or the HGA. The micro-actuator enables, for example, the use of a smaller recording track pitch, and can increase the “tracks-per-inch” (TPI) value by 50% for the disk drive unit, as well as provide an advantageous reduction in the head seeking and settling time. Thus, the PZT micro-actuator enables the disk drive device to have a significant increase in the surface recording density of the information storage disks used therein.
Referring to FIGS. 1a and 1b, the PZT micro-actuator comprises two PZT elements denoted by reference number 120 and mounted within the HGA 106 which further includes the slider 103 and a suspension 110 to support the slider 103 and the PZT elements 120 of the micro-actuator. The suspension 110 comprises a flexure 111, a slider support 112 with a bump 112a formed thereon, a metal base 113 and a load beam 114 with a dimple 114a formed thereon. The slider 103 is partially mounted on the slider support 112 with the bump 112a supporting the center of the back surface of the slider 103. Specifically, the flexure 111 provides a plurality of traces thereon. The traces of the flexure 111 couple the slider support 112 and the metal base 113. The flexure 111 further forms a tongue region 111a for positioning the two PZT elements 120 of the micro-actuator. Referring to FIG. 1c, when a voltage is input to the two thin film PZT elements 120 of the PZT micro-actuator, one of the PZT elements may contract as shown by arrow D while the other may expand as shown by arrow E. This will generate a rotation torque that causes the slider support 112 to rotate in the arrowed direction C and, in turn, makes the slider 103 move on the disk. In such case, the dimple 114a of the load beam 114 works with the bump 112a of the slider support 112, that is, the slider 103 together with the slider support 112 rotates against the dimple 114a, which keeps the load force from the load beam 114 evenly applying to the center of the slider 103, thus ensuring the slider 103 a good fly performance, supporting the head with a good flying stability.
FIG. 2a is a plane view of the PZT elements 120 of the HGA 106 shown in FIG. 1b. FIG. 2b is a sectional view taken along line A-A of FIG. 2a. Referring to FIGS. 2a-2b, the PZT element 120 includes a left PZT element 120a and a right PZT element 120b which are arranged symmetrically. The left PZT element 120a provides two pair of electrical pads 120′a. The right PZT element 120b provides two pair of electrical pads 120′b. The surface of the left PZT element 120a and the right PZT element 120b are coated with resin 121. The resin 121 comprises an adhesive connection portion 121′. The adhesive connection portion 121′ is positioned between the left PZT element 120a and the right PZT element 120b in order to physically connect the left PZT element 120a and the right PZT element 120b. The two PZT elements 120a, 120b both have a first electrode-piezoelectric combination structure and a second electrode-piezoelectric combination structure. The first electrode-piezoelectric combination structure is connected with the second electrode-piezoelectric combination structure by adhesive. Specifically, the first electrode-piezoelectric combination structure comprises a first PZT layer 123, a first electrode layer 122 and a second electrode layer 124 which are laminated on two opposite surfaces of the PZT layer 123. The second electrode-piezoelectric combination structure comprises a second PZT layer 127, a third electrode layer 126 and a fourth electrode layer 128 which are laminated on two opposite surfaces of the PZT layer 127. An adhesive layer 125 bonds the second electrode layer 124 and the third electrode layer 126 thus to connect the first electrode-piezoelectric combination structure and a second electrode-piezoelectric combination structure together. One pair of the electrical pads 120′a/120′b of the left/right PZT element 120a/120b are respectively positioned on the first electrode layer 122 of the first electrode-piezoelectric combination structure and the fourth electrode layer 128 of the second electrode-piezoelectric combination structure of the left/right PZT element 120a/120b. The other pair of the electrical pads 120′a/120′b of the left/right PZT element 120a/120b are respectively positioned on the second electrode layer 124 of the first electrode-piezoelectric combination structure and the third electrode layer 126 of the second electrode-piezoelectric combination structure of the left/right PZT element 120a/120b. 
FIGS. 3a-3h illustrate the prior method of manufacturing the PZT element 120a/120b. As shown in FIG. 3a, the first electrode layer 122, the first PZT layer 123 and the second electrode layer 124 are sequentially laminated on a first substrate 155. The fourth electrode layer 128, the second PZT layer 127 and the third electrode layer 126 are sequentially laminated on a second substrate 166. As shown in FIG. 3b, the adhesive layer 125 bonds the second electrode layer 124 and the third electrode layer 126 thus to form multiple layers of electrode-piezoelectric combination structures. As shown in FIG. 3c, the first substrate 155 is removed. Herein removing the first substrate 155 could be performed by chemical etching process or photolithography process or ion sputtering method. As shown in FIG. 3d, the multiple layers of electrode-piezoelectric combination structures are proceeded with shape processing treatment on the second substrate 166 using photolithography process or etching process to form initial left/right PZT element of predetermined shape. At the same time, the first electrode layer 122, the second electrode layer 124, the third electrode layer 126 and the fourth electrode layer 128 respectively forms a electrical pad 120′a/120′b (not shown). As shown in FIGS. 3e-3f, the resin 121 covers the surface of the initial left/right PZT element, and the adhesive connection portion 121′ of the resin 121 bonds between the initial left and right PZT elements. As shown in FIGS. 3g-3h, the second substrate 166 is removed and thus the left, right PZT element 120a, 120b with two PZT layer 123, 127 are formed. As shown, the PZT element 120 has the left PZT element 120a and the right PZT element 120b which are connected together.
However, the PZT element 120a/120b manufactured by above-mentioned method has a small insulation resistance, a high reject rate and a high manufacture cost. The following will take the first electrode-piezoelectric combination structure as an example to illustrate the reason. Because of the restriction of the manufacturing process, especially limitation of chimerical etching control and contamination control, the sides of the first electrode layer 122 and the second electrode layer 124, which are parallel to the laminating direction of the first electrode-piezoelectric combination structure, are aligned up-and-down. This causes the insulation resistance between the first electrode layer 122 and the second electrode layer 124 of the first PZT layer 123 small, thereby the reject rate of PZT element is high and the manufacture cost is high. The same problems also occur in the second electrode-piezoelectric combination structure.
Hence, it is desired to provide an improved PZT element and manufacturing method thereof, a head gimbal assembly with the PZT element, a disk drive unit with the head gimbal assembly to solve the above-mentioned problems.